Chapter 27
Ecological Subregions of the United States

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Pacific Gulf Coastal Forest - Meadow

Three Sections have been delineated in this Province:

These Sections are located in southern Alaska, bordering the Gulf of Alaska, and include part of Kodiak Island. The area of these Section is about 35,000 mi2 (68,000 km2).

Section M245A--Northern Gulf

Geomorphology. This area includes Afognak Island, Prince William Sound, coastal lowlands of Copper River Delta, and Yakutat Forelands. The foreland areas consist of alluvial fans, uplifted estuaries, morainal deposits, dunes, river deltas, and terraces. Crustal uplifting has created terraces or dunes that run parallel to the coastline. Erosion by glacial outburst floods dissect the forelands and dominate landscape patterns. The headlands within Prince William Sound and Afognak Island are erosional bedrock features that end as sea cliffs at the water's edge where little to no deposition occurs except in bays and shallow estuaries. Elevation ranges from sea level to 500 ft (150 m).

Lithology and Stratigraphy. The area consists of Quaternary to recent sediments in the foreland and delta areas. Uplands consist of near-shore oceanic rocks of the Prince William, Chugach, and Yakutat terranes of interbedded sedimentary, volcanic rock types with ages from Palezoic to upper Mesozoic. Slate and graywacke are prevalent rocks.

Soil Taxa. Soils near the mountains formed in gravelly and stony morainal deposits. Soils of river deltas, terraces, alluvial fans, and flood plains form in water-laden sands and silts. Poorly drained depressions are filled wth peat. Typical soils are Terric Cryohemists, Humic Cryorthods, Humic Lithic Cryorthods, and Andic Humicryods.

Potential Natural Vegetation. Coastal subpolar rainforests of western hemlock and Sitka spruce are characteristic in areas with better soil drainage. Along the coastline, areas with high water tables support sphagnum mosses, sedges, and willows, which foster peatland development. Alder, cottonwood, and birch dominate the low-lying areas and along major river channels.

Fauna. The entire population of dusky Canada geese nests within this Section. Trumpeter swans are considered a common breeder, especially on the Copper River Delta. Bald eagles, marbled murrelets, and Kittlitz's murrelets utilize forested habitats adjacent to the waters of Prince William Sound. Bonaparte's gulls are commonly observed. Sea otters and Steller's sea lions are common throughout Prince William Sound. Mountain goats occupy habitats from alpine areas into the forested slopes. Sitka black-tailed deer were introduced from 1916 through 1923 and now occupy most of the islands and the adjacent mainland of Prince William Sound. Roosevelt elk were introduced to Afognak Island in 1929. From 1949 through 1957 moose were introduced to the Copper River Delta. Rough-skinned newts and boreal toads have been reported from this Section. Pink and chum salmon are the major salmon species present. The Copper River supports a significant population of sockeye salmon. Both anadromous and nonanadromous populations of dolly varden are present in this Section.

Climate. Average annual precipitation ranges from 30 to 160 in (760 to 4,060 mm). Average annual temperature ranges from 30 to 42 oF (-1 to 6 oC). The growing season lasts approximately from May 10 to September 30.

Surface Water Characteristics. Most streams head in glaciers from mountains of adjoining areas and are low-gradient braided systems with overbank flooding and glacial outburst floods common in some watersheds. Wetlands occupy approximately 30 percent of the area, with the majority in Copper River Delta, Yakutat, and other lowland areas.

Disturbance Regimes. Wildfire occurrence is rare. Glacial outburst floods and tectonic events have changed the character of many of the areas. Land subsidence or uplifting abruptly changes successional pathways and accelerated erosion or deposition.

Land Use. Human use is common, with commercial timber harvesting, fishing, mining, and recreational activities occurring year around. Roads, airstrips, and abandoned rail lines attest to the significant human presence, all of which affect local ecosystems to varying degrees.

Cultural Ecology. Alutiiq Eskimos (west), Eyaks (central), and Tlingits (east) were original inhabitants.

Compiled by Alaska Region.

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Section M245B--Northern Alexander Archipelago

Geomorphology. This Section includes Baranof, Chichagof, and Admiralty Islands, and the portion of the mainland below the permanent snowfields in southeast Alaska. These areas have rugged topography with many long and broad U-shaped glaciated valleys, many of which terminate at tidewater. Side slopes are very steep and exposed bedrock is common along the glacially scoured valley walls. The rolling moraine landforms dominate the low hills and valley bottoms. Elevation ranges from sea level to over 3,280 ft (1,000 m).

Lithology and Stratigraphy. The geology is very complex, consisting of the Craig and Admiralty subterranes, and the Wrangellia, Chugach, and Taku terranes, all of which are volcanic islands-arcs and continental fragments. Most rock types are Jurassic to Mesozoic deposits of sedimentary and volcanic rock types. Many of the assemblages have been metamorphosed, faulted, or folded, and the trending of most faults is northwesterly.

Soil Taxa. Predominant soils are Terric Cryohemists, Humic Cryorthods, Humic Lithic Cryorthods, and Andic Humicryods. Most of the soils on the steep slopes are formed in colluvial or landslide materials. Poorly drained depressions or low-lying areas are peatlands.

Potential Natural Vegetation. Perhumid rainforests of Sitka spruce and western hemlock predominate. Water-tolerant plants, such as sphagnum moss, sedges, bog kalmia, and shore pine, occur in peatlands. Alpine tundra heath meadows and barrens occur at higher elevations.

Fauna. Bald eagles and marbled murrelets nest in forested areas on the islands and coastal mainland in this Section. Vancouver Canada geese nest and winter throughout southeast Alaska. Red-breasted sapsuckers, Pacific-slope flycatchers, golden-crowned kinglets, and red and white-winged crossbills are common breeders in the forests of this Section. Blue grouse are common throughout the area. Northern water shrews, deer mice, and long-tailed voles are commonly present. Porcupines are common on the mainland; river otters and mink are found throughout the Section. Marten were introduced to Baranof Island in 1934 and to Chichagof Island from 1949 through 1952. Red squirrels were introduced to these islands in 1930. Mountain goats occur on the mainland and were introduced to Baranof Island in 1923. Sitka black-tailed deer occur throughout the Section. Brown bear are present in high densities on Admiralty, Baranof, and Chichagof islands and in lower densities on the mainland. Black bears and gray wolves only occur on the mainland. Rough-skinned newts and boreal toads occur in this Section. King salmon are associated with the major mainland rivers. Pink salmon are the most numerous of the salmon species throughout the Section. Dolly varden are the most widely distributed resident fish.

Climate. Average annual precipitation ranges from 70 to 220 in (1,780 to 5,590 mm). Average annual temperature ranges from 40 to 42 oF (4 to 6 oC). The growing season is from about May 1 to September 30. Killing frost can occur at any time in the higher elevations.

Surface Water Characteristics. The area has abundant precipitation and many small lakes and streams. Well-drained soils are generally at or near saturation most of the year. Most of the streams and river terminate in bays or estuaries; and fjords are rare. Wetlands occupy over 35 percent of the area.

Disturbance Regimes. Wildfire is rare, but landslides and avalanches occur abundantly. These disturbances keep vegetation in early seral stages along steeper valley walls. The outer islands are subject to intense winds from winter storms, causing much damage to forest stands.

Land Use. Human activity in the form of timber harvesting and road building is common on most of the islands, with the exception of Admiralty Island.

Cultural Ecology. This is the historic range of the Tlingit Indians.

Compiled by Alaska Region.

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Section M245C--Southern Alexander Archipelago

Geomorphology. This Section includes all the islands below Fredrick Sound, as well as the mainland south of the Stikine River corridor below the permanent snowfields in southeast Alaska. Most of the area is rugged mountains with many broad, U-shaped, glaciated valleys which terminate as fjords at tidewater. Tidewater glaciers are infrequent in this Section. Elevation ranges from sea level to over 3,280 ft (1,000 m).

Lithology and Stratigraphy. The geology is very complex, consisting of volcanic islands and continental fragments of the Craig subterrane, Admiralty subterrane, and Taku terrane. Most rock types are Jurassic to Mesozoic deposits of sedimentary and volcanic rock types. Many of the assemblages have been metamorphosed, faulted, or folded, and the trending of most faults is northwesterly.

Soil Taxa. Predominant soils are Terric Cryohemists, Humic Cryorthods, Humic Lithic Cryorthods, and Andic Humicryods. Most of the soils on the steep slopes are formed in colluvial or landslide materials. Poorly drained depressions or low-lying areas are peatlands.

Potential Natural Vegetation. Coastal perhumid rainforests of Sitka spruce and western hemlock predominate. The northern limits of western red cedar and salal correspond to the northern boundary of this Section. Hydric vegetation of sphagnum moss, sedges, and willows predominate on peatlands. Some alpine heath meadows occur on the highest mountains.

Fauna. Bald eagles and marbled murrelets nest in forested areas on the islands and coastal mainland in this Section. Vancouver Canada geese nest and winter throughout southeast Alaska. Red-breasted sapsuckers, Pacific-slope flycatchers, golden-crowned kinglets, and red and white-winged crossbills are common breeders in the forests of this Section. Blue grouse are common throughout the area. Northern water shrews, deer mice, and long-tailed voles are commonly present. Porcupines are common on the mainland; river otters and mink are found throughout the Section. Marten were introduced to Prince of Wales Island in 1934. Mountain goats occur on the mainland and were introduced to Revillagigedo Island in 1983 and 1991. Sitka black-tailed deer occur throughout the Section. Rocky Mountain and Roosevelt elk were introduced to Etolin Island in 1987. Brown bear are present in low densities on the mainland, but not on the islands of this Section. Gray wolves and black bears are present throughout this area. Rough-skinned newts, northwest salamanders, long-toed salamanders, wood frogs, spotted frogs, and boreal toads occur in this Section. King salmon are associated with the major mainland rivers. Pink and silver are the most numerous salmon throughout the Section. Dolly varden are the most widely distributed resident fish.

Climate. Average annual precipitation ranges from 75 to 220 in (1,900 to 5,590 mm). Average annual temperature ranges from 42 to 46 oF (6 to 8 oC). The growing season lasts from about May 1 to September 30.

Surface Water Characteristics. The area has abundant precipitation and many small lakes and streams. Soils are generally at or near saturation most of the year. Most of the streams and rivers terminate in bays or estuaries, and fjords are common. Wetlands occupy 35 percent of the area.

Disturbance Regimes. Wildfire occurs only during drought periods. Landslides and avalanches are frequent on the steeper, intergorge walls, maintaining early successional communities. The outer islands are subject to extreme winds from winter storms. In turn, windthrow is common in forests along outer coasts.

Land Use. The presence of human activity in the form of timber harvesting and road building is common in most areas, except for the Misty Fjords National Monument.

Cultural Ecology. Both Tlingit and Haida Tribes reside here.

Compiled by Alaska Region.

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